diff --git a/e2e/__cases__/allow-js/tsconfig.json b/e2e/__cases__/allow-js/tsconfig.json
index 26f31aa261..c052135751 100644
--- a/e2e/__cases__/allow-js/tsconfig.json
+++ b/e2e/__cases__/allow-js/tsconfig.json
@@ -1,6 +1,7 @@
 {
   "compilerOptions": {
     "target": "es5",
-    "allowJs": true
+    "allowJs": true,
+    "outDir": "$$ts-jest$$"
   }
 }
diff --git a/e2e/__monorepos__/simple/with-dependency/package.json b/e2e/__monorepos__/simple/with-dependency/package.json
index d0c64b6486..1f4d55b21a 100644
--- a/e2e/__monorepos__/simple/with-dependency/package.json
+++ b/e2e/__monorepos__/simple/with-dependency/package.json
@@ -31,7 +31,8 @@
     "globals": {
       "ts-jest": {
         "diagnostics": true,
-        "tsConfig": "<rootDir>/tsconfig.json"
+        "tsConfig": "<rootDir>/tsconfig.json",
+        "compilerHost": true
       }
     }
   },
diff --git a/e2e/__monorepos__/simple/with-dependency/tsconfig.json b/e2e/__monorepos__/simple/with-dependency/tsconfig.json
index e2a32abfa8..65f41ccd82 100644
--- a/e2e/__monorepos__/simple/with-dependency/tsconfig.json
+++ b/e2e/__monorepos__/simple/with-dependency/tsconfig.json
@@ -13,7 +13,8 @@
     "downlevelIteration": true,
     "strict": true,
     "moduleResolution": "node",
-    "esModuleInterop": true
+    "esModuleInterop": true,
+    "incremental": true
   },
   "include": [
     "./src"
diff --git a/e2e/__tests__/__snapshots__/logger.test.ts.snap b/e2e/__tests__/__snapshots__/logger.test.ts.snap
index 82c1d4ab21..6ffc58bce4 100644
--- a/e2e/__tests__/__snapshots__/logger.test.ts.snap
+++ b/e2e/__tests__/__snapshots__/logger.test.ts.snap
@@ -19,21 +19,21 @@ Array [
   "[level:20] readTsConfig(): reading <cwd>/tsconfig.json",
   "[level:20] normalized typescript config",
   "[level:20] processing <cwd>/Hello.spec.ts",
-  "[level:20] creating typescript compiler (language service)",
   "[level:20] file caching disabled",
-  "[level:20] creating language service",
+  "[level:20] compileUsingLanguageService(): creating language service",
   "[level:20] readThrough(): no cache",
-  "[level:20] getOutput(): compiling using language service",
-  "[level:20] updateMemoryCache()",
+  "[level:20] updateMemoryCache() for language service",
+  "[level:20] compiler rebuilt Program instance when getting output",
   "[level:20] visitSourceFileNode(): hoisting",
-  "[level:20] getOutput(): computing diagnostics",
+  "[level:20] getOutput(): computing diagnostics for language service",
+  "[level:20] invariant: Is service.getProject() identical before and after getting emit output and diagnostics? (should always be true)  true",
   "[level:20] computing cache key for <cwd>/Hello.ts",
   "[level:20] processing <cwd>/Hello.ts",
   "[level:20] readThrough(): no cache",
-  "[level:20] getOutput(): compiling using language service",
-  "[level:20] updateMemoryCache()",
+  "[level:20] updateMemoryCache() for language service",
   "[level:20] visitSourceFileNode(): hoisting",
-  "[level:20] getOutput(): computing diagnostics",
+  "[level:20] getOutput(): computing diagnostics for language service",
+  "[level:20] invariant: Is service.getProject() identical before and after getting emit output and diagnostics? (should always be true)  true",
 ]
 `;
 
@@ -60,22 +60,22 @@ Array [
   "[level:20] loaded module babel-jest",
   "[level:20] patching babel-jest",
   "[level:20] checking version of babel-jest: OK",
-  "[level:20] creating typescript compiler (language service)",
   "[level:20] file caching disabled",
-  "[level:20] creating language service",
+  "[level:20] compileUsingLanguageService(): creating language service",
   "[level:20] readThrough(): no cache",
-  "[level:20] getOutput(): compiling using language service",
-  "[level:20] updateMemoryCache()",
+  "[level:20] updateMemoryCache() for language service",
+  "[level:20] compiler rebuilt Program instance when getting output",
   "[level:20] visitSourceFileNode(): hoisting",
-  "[level:20] getOutput(): computing diagnostics",
+  "[level:20] getOutput(): computing diagnostics for language service",
+  "[level:20] invariant: Is service.getProject() identical before and after getting emit output and diagnostics? (should always be true)  true",
   "[level:20] calling babel-jest processor",
   "[level:20] computing cache key for <cwd>/Hello.ts",
   "[level:20] processing <cwd>/Hello.ts",
   "[level:20] readThrough(): no cache",
-  "[level:20] getOutput(): compiling using language service",
-  "[level:20] updateMemoryCache()",
+  "[level:20] updateMemoryCache() for language service",
   "[level:20] visitSourceFileNode(): hoisting",
-  "[level:20] getOutput(): computing diagnostics",
+  "[level:20] getOutput(): computing diagnostics for language service",
+  "[level:20] invariant: Is service.getProject() identical before and after getting emit output and diagnostics? (should always be true)  true",
   "[level:20] calling babel-jest processor",
 ]
 `;
@@ -104,22 +104,22 @@ Array [
   "[level:20] loaded module babel-jest",
   "[level:20] patching babel-jest",
   "[level:20] checking version of babel-jest: OK",
-  "[level:20] creating typescript compiler (language service)",
   "[level:20] file caching disabled",
-  "[level:20] creating language service",
+  "[level:20] compileUsingLanguageService(): creating language service",
   "[level:20] readThrough(): no cache",
-  "[level:20] getOutput(): compiling using language service",
-  "[level:20] updateMemoryCache()",
+  "[level:20] updateMemoryCache() for language service",
+  "[level:20] compiler rebuilt Program instance when getting output",
   "[level:20] visitSourceFileNode(): hoisting",
-  "[level:20] getOutput(): computing diagnostics",
+  "[level:20] getOutput(): computing diagnostics for language service",
+  "[level:20] invariant: Is service.getProject() identical before and after getting emit output and diagnostics? (should always be true)  true",
   "[level:20] calling babel-jest processor",
   "[level:20] computing cache key for <cwd>/Hello.ts",
   "[level:20] processing <cwd>/Hello.ts",
   "[level:20] readThrough(): no cache",
-  "[level:20] getOutput(): compiling using language service",
-  "[level:20] updateMemoryCache()",
+  "[level:20] updateMemoryCache() for language service",
   "[level:20] visitSourceFileNode(): hoisting",
-  "[level:20] getOutput(): computing diagnostics",
+  "[level:20] getOutput(): computing diagnostics for language service",
+  "[level:20] invariant: Is service.getProject() identical before and after getting emit output and diagnostics? (should always be true)  true",
   "[level:20] calling babel-jest processor",
 ]
 `;
@@ -143,21 +143,21 @@ Array [
   "[level:20] readTsConfig(): reading <cwd>/tsconfig.json",
   "[level:20] normalized typescript config",
   "[level:20] processing <cwd>/Hello.spec.ts",
-  "[level:20] creating typescript compiler (language service)",
   "[level:20] file caching disabled",
-  "[level:20] creating language service",
+  "[level:20] compileUsingLanguageService(): creating language service",
   "[level:20] readThrough(): no cache",
-  "[level:20] getOutput(): compiling using language service",
-  "[level:20] updateMemoryCache()",
+  "[level:20] updateMemoryCache() for language service",
+  "[level:20] compiler rebuilt Program instance when getting output",
   "[level:20] visitSourceFileNode(): hoisting",
-  "[level:20] getOutput(): computing diagnostics",
+  "[level:20] getOutput(): computing diagnostics for language service",
+  "[level:20] invariant: Is service.getProject() identical before and after getting emit output and diagnostics? (should always be true)  true",
   "[level:20] computing cache key for <cwd>/Hello.ts",
   "[level:20] processing <cwd>/Hello.ts",
   "[level:20] readThrough(): no cache",
-  "[level:20] getOutput(): compiling using language service",
-  "[level:20] updateMemoryCache()",
+  "[level:20] updateMemoryCache() for language service",
   "[level:20] visitSourceFileNode(): hoisting",
-  "[level:20] getOutput(): computing diagnostics",
+  "[level:20] getOutput(): computing diagnostics for language service",
+  "[level:20] invariant: Is service.getProject() identical before and after getting emit output and diagnostics? (should always be true)  true",
 ]
 `;
 
diff --git a/package.json b/package.json
index e437ec792a..41e64c1b86 100644
--- a/package.json
+++ b/package.json
@@ -134,6 +134,6 @@
     ]
   },
   "engines": {
-    "node": ">= 6"
+    "node": ">= 8"
   }
 }
diff --git a/src/__helpers__/fakers.ts b/src/__helpers__/fakers.ts
index a803c481ac..c2e23369a6 100644
--- a/src/__helpers__/fakers.ts
+++ b/src/__helpers__/fakers.ts
@@ -1,6 +1,8 @@
 import { Config } from '@jest/types'
 import { resolve } from 'path'
 
+import { createCompiler } from '../compiler/instance'
+import { ConfigSet } from '../config/config-set'
 import { BabelConfig, TsJestConfig, TsJestGlobalOptions } from '../types'
 import { ImportReasons } from '../util/messages'
 
@@ -10,52 +12,10 @@ export function filePath(relPath: string): string {
 
 export const rootDir = filePath('')
 
-export function transpiledTsSource() {
-  return `
-"use strict";
-var __importDefault = (this && this.__importDefault) || function (mod) {
-    return (mod && mod.__esModule) ? mod : { "default": mod };
-};
-var upper_1 = __importDefault(require("./upper"));
-var lower_1 = __importDefault(require("./lower"));
-jest.mock('./upper', function () { return function (s) { return s.toUpperCase(); }; });
-describe('hello', function () {
-    test('my test', function () {
-        expect(upper_1.default('hello')).toBe('HELLO');
-        expect(lower_1.default('HELLO')).toBe('hello');
-        jest.mock('./lower', function () { return function (s) { return s.toLowerCase(); }; });
-    });
-});
-`
-}
-
-export function htmlSource() {
-  return `
-<div>
-  <span>some text with \`backtick\`</span>
-</div>
-`
-}
-
-export function typescriptSource() {
-  return `
-import upper from './upper';
-import lower from './lower';
-
-jest.mock('./upper', () => (s) => s.toUpperCase());
-
-describe('hello', () => {
-  test('my test', () => {
-    expect(upper('hello')).toBe('HELLO');
-    expect(lower('HELLO')).toBe('hello');
-    jest.mock('./lower', () => (s) => s.toLowerCase());
-  });
-});
-`
-}
-
 export function tsJestConfig(options?: Partial<TsJestConfig>): TsJestConfig {
   return {
+    compilerHost: false,
+    emit: false,
     isolatedModules: false,
     compiler: 'typescript',
     transformers: [],
@@ -68,7 +28,7 @@ export function tsJestConfig(options?: Partial<TsJestConfig>): TsJestConfig {
   }
 }
 
-export function jestConfig<T extends Config.ProjectConfig>(
+export function getJestConfig<T extends Config.ProjectConfig>(
   options?: Partial<Config.InitialOptions | Config.ProjectConfig>,
   tsJestOptions?: TsJestGlobalOptions,
 ): T {
@@ -93,3 +53,23 @@ export function babelConfig<T extends BabelConfig>(options?: BabelConfig): T {
 export function importReason(text = '[[BECAUSE]]'): ImportReasons {
   return text as any
 }
+
+// not really unit-testing here, but it's hard to mock all those values :-D
+export function makeCompiler({
+  jestConfig,
+  tsJestConfig,
+  parentConfig,
+}: {
+  jestConfig?: Partial<Config.ProjectConfig>
+  tsJestConfig?: TsJestGlobalOptions
+  parentConfig?: TsJestGlobalOptions
+} = {}) {
+  tsJestConfig = { ...tsJestConfig }
+  tsJestConfig.diagnostics = {
+    ...(tsJestConfig.diagnostics as any),
+    pretty: false,
+  }
+  const cs = new ConfigSet(getJestConfig(jestConfig, tsJestConfig), parentConfig)
+
+  return createCompiler(cs)
+}
diff --git a/src/__snapshots__/compiler.spec.ts.snap b/src/__snapshots__/compiler.spec.ts.snap
deleted file mode 100644
index f6496bce1d..0000000000
--- a/src/__snapshots__/compiler.spec.ts.snap
+++ /dev/null
@@ -1,53 +0,0 @@
-// Jest Snapshot v1, https://goo.gl/fbAQLP
-
-exports[`allowJs should compile js file 1`] = `
-  ===[ FILE: src/compiler.spec.ts.test.js ]=======================================
-  "use strict";
-  Object.defineProperty(exports, "__esModule", { value: true });
-  exports.default = 42;
-  //# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJmaWxlIjoiPGN3ZD4vc3JjL2NvbXBpbGVyLnNwZWMudHMudGVzdC5qcyIsIm1hcHBpbmdzIjoiOztBQUFBLGtCQUFlLEVBQUUsQ0FBQSIsIm5hbWVzIjpbXSwic291cmNlcyI6WyI8Y3dkPi9zcmMvY29tcGlsZXIuc3BlYy50cy50ZXN0LmpzIl0sInNvdXJjZXNDb250ZW50IjpbImV4cG9ydCBkZWZhdWx0IDQyIl0sInZlcnNpb24iOjN9
-  ===[ INLINE SOURCE MAPS ]=======================================================
-  file: <cwd>/src/compiler.spec.ts.test.js
-  mappings: ';;AAAA,kBAAe,EAAE,CAAA'
-  names: []
-  sources:
-    - <cwd>/src/compiler.spec.ts.test.js
-  sourcesContent:
-    - export default 42
-  version: 3
-  ================================================================================
-`;
-
-exports[`cache should use the cache 3`] = `
-  ===[ FILE: src/compiler.spec.ts ]===============================================
-  console.log("hello");
-  //# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJmaWxlIjoiPGN3ZD4vc3JjL2NvbXBpbGVyLnNwZWMudHMiLCJtYXBwaW5ncyI6IkFBQUEsT0FBTyxDQUFDLEdBQUcsQ0FBQyxPQUFPLENBQUMsQ0FBQSIsIm5hbWVzIjpbXSwic291cmNlcyI6WyI8Y3dkPi9zcmMvY29tcGlsZXIuc3BlYy50cyJdLCJzb3VyY2VzQ29udGVudCI6WyJjb25zb2xlLmxvZyhcImhlbGxvXCIpIl0sInZlcnNpb24iOjN9
-  ===[ INLINE SOURCE MAPS ]=======================================================
-  file: <cwd>/src/compiler.spec.ts
-  mappings: 'AAAA,OAAO,CAAC,GAAG,CAAC,OAAO,CAAC,CAAA'
-  names: []
-  sources:
-    - <cwd>/src/compiler.spec.ts
-  sourcesContent:
-    - console.log("hello")
-  version: 3
-  ================================================================================
-`;
-
-exports[`isolatedModules should compile using transpileModule 1`] = `
-  ===[ FILE: src/compiler.spec.ts ]===============================================
-  "use strict";
-  Object.defineProperty(exports, "__esModule", { value: true });
-  exports.default = 42;
-  //# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJmaWxlIjoiPGN3ZD4vc3JjL2NvbXBpbGVyLnNwZWMudHMiLCJtYXBwaW5ncyI6Ijs7QUFBQSxrQkFBZSxFQUFFLENBQUEiLCJuYW1lcyI6W10sInNvdXJjZXMiOlsiPGN3ZD4vc3JjL2NvbXBpbGVyLnNwZWMudHMiXSwic291cmNlc0NvbnRlbnQiOlsiZXhwb3J0IGRlZmF1bHQgNDIiXSwidmVyc2lvbiI6M30=
-  ===[ INLINE SOURCE MAPS ]=======================================================
-  file: <cwd>/src/compiler.spec.ts
-  mappings: ';;AAAA,kBAAe,EAAE,CAAA'
-  names: []
-  sources:
-    - <cwd>/src/compiler.spec.ts
-  sourcesContent:
-    - export default 42
-  version: 3
-  ================================================================================
-`;
diff --git a/src/compiler.spec.ts b/src/compiler.spec.ts
deleted file mode 100644
index 4217605c88..0000000000
--- a/src/compiler.spec.ts
+++ /dev/null
@@ -1,163 +0,0 @@
-// tslint:disable:max-line-length
-import { Config } from '@jest/types'
-import { LogLevels } from 'bs-logger'
-import { removeSync, writeFileSync } from 'fs-extra'
-
-import * as fakers from './__helpers__/fakers'
-import { logTargetMock } from './__helpers__/mocks'
-import { tempDir } from './__helpers__/path'
-import ProcessedSource from './__helpers__/processed-source'
-import { createCompiler } from './compiler'
-import { ConfigSet } from './config/config-set'
-import { TsJestGlobalOptions } from './types'
-
-const logTarget = logTargetMock()
-
-// not really unit-testing here, but it's hard to mock all those values :-D
-function makeCompiler({
-  jestConfig,
-  tsJestConfig,
-  parentConfig,
-}: {
-  jestConfig?: Partial<Config.ProjectConfig>
-  tsJestConfig?: TsJestGlobalOptions
-  parentConfig?: TsJestGlobalOptions
-} = {}) {
-  tsJestConfig = { ...tsJestConfig }
-  tsJestConfig.diagnostics = {
-    ...(tsJestConfig.diagnostics as any),
-    pretty: false,
-  }
-  const cs = new ConfigSet(fakers.jestConfig(jestConfig, tsJestConfig), parentConfig)
-  return createCompiler(cs)
-}
-
-beforeEach(() => {
-  logTarget.clear()
-})
-
-describe('typings', () => {
-  const compiler = makeCompiler({ tsJestConfig: { tsConfig: false } })
-  it('should report diagnostics related to typings', () => {
-    expect(() =>
-      compiler.compile(
-        `
-const f = (v: number) => v
-const t: string = f(5)
-const v: boolean = t
-`,
-        'foo.ts',
-      ),
-    ).toThrowErrorMatchingInlineSnapshot(`
-"TypeScript diagnostics (customize using \`[jest-config].globals.ts-jest.diagnostics\` option):
-foo.ts(3,7): error TS2322: Type 'number' is not assignable to type 'string'.
-foo.ts(4,7): error TS2322: Type 'string' is not assignable to type 'boolean'."
-`)
-  })
-})
-
-describe('source-maps', () => {
-  const compiler = makeCompiler({ tsJestConfig: { tsConfig: false } })
-  it('should have correct source maps', () => {
-    const source = 'const f = (v: number) => v\nconst t: number = f(5)'
-    const compiled = compiler.compile(source, __filename)
-    const processed = new ProcessedSource(compiled, __filename)
-    // const expectedFileName = relativeToRoot(__filename)
-    const expectedFileName = __filename
-    expect(processed.outputSourceMaps).toMatchObject({
-      file: expectedFileName,
-      sources: [expectedFileName],
-      sourcesContent: [source],
-    })
-  })
-})
-
-describe('cache', () => {
-  const tmp = tempDir('compiler')
-  const compiler = makeCompiler({
-    jestConfig: { cache: true, cacheDirectory: tmp },
-    tsJestConfig: { tsConfig: false },
-  })
-  const source = 'console.log("hello")'
-
-  it('should use the cache', () => {
-    const compiled1 = compiler.compile(source, __filename)
-    expect(logTarget.filteredLines(LogLevels.debug, Infinity)).toMatchInlineSnapshot(`
-Array [
-  "[level:20] readThrough(): cache miss
-",
-  "[level:20] getOutput(): compiling using language service
-",
-  "[level:20] updateMemoryCache()
-",
-  "[level:20] visitSourceFileNode(): hoisting
-",
-  "[level:20] getOutput(): computing diagnostics
-",
-  "[level:20] readThrough(): writing caches
-",
-]
-`)
-
-    logTarget.clear()
-    const compiled2 = compiler.compile(source, __filename)
-    expect(logTarget.lines).toMatchInlineSnapshot(`
-Array [
-  "[level:20] readThrough(): cache hit
-",
-]
-`)
-
-    expect(new ProcessedSource(compiled1, __filename)).toMatchSnapshot()
-    expect(compiled2).toBe(compiled1)
-  })
-})
-
-describe('isolatedModules', () => {
-  const compiler = makeCompiler({ tsJestConfig: { isolatedModules: true, tsConfig: false } })
-  const spy = jest.spyOn(require('typescript'), 'transpileModule')
-  afterAll(() => {
-    spy.mockRestore()
-  })
-  it('should compile using transpileModule', () => {
-    const compiled = compiler.compile('export default 42', __filename)
-    expect(new ProcessedSource(compiled, __filename)).toMatchSnapshot()
-    expect(spy).toHaveBeenCalled()
-  })
-})
-
-describe('allowJs', () => {
-  const compiler = makeCompiler({ tsJestConfig: { tsConfig: { allowJs: true } } })
-  const fileName = `${__filename}.test.js`
-  afterAll(() => {
-    removeSync(fileName)
-  })
-  it('should compile js file', () => {
-    const source = 'export default 42'
-    writeFileSync(fileName, source, 'utf8')
-    const compiled = compiler.compile(source, fileName)
-    const processed = new ProcessedSource(compiled, fileName)
-    expect(processed).toMatchSnapshot()
-  })
-})
-
-describe('getTypeInfo', () => {
-  const compiler = makeCompiler({ tsJestConfig: { tsConfig: false } })
-  const source = `
-type MyType {
-  /** the prop 1! */
-  p1: boolean
-}
-const val: MyType = {} as any
-console.log(val.p1/* <== that */)
-`
-  it('should get correct type info', () => {
-    const ti = compiler.getTypeInfo(source, __filename, source.indexOf('/* <== that */') - 1)
-    // before TS 3.1 the comment had an extra tailing space
-    ti.comment = ti.comment.trim()
-    expect(ti).toEqual({
-      comment: 'the prop 1!',
-      name: '(property) p1: boolean',
-    })
-  })
-})
diff --git a/src/compiler.ts b/src/compiler.ts
deleted file mode 100644
index 484ab17414..0000000000
--- a/src/compiler.ts
+++ /dev/null
@@ -1,363 +0,0 @@
-/**
- * This code is heavilly inspired from
- * https://github.com/JsCommunity/make-error/blob/v1.3.4/index.js
- * ...but more modified than expected :-D
- * Below is the original license anyway:
- *
- * ---
- *
- * The MIT License (MIT)
- *
- * Copyright (c) 2014 Blake Embrey (hello@blakeembrey.com)
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-import { LogContexts, LogLevels, Logger } from 'bs-logger'
-import bufferFrom = require('buffer-from')
-import stableStringify = require('fast-json-stable-stringify')
-import { readFileSync, writeFileSync } from 'fs'
-import { defaults as JestDefaults, replaceRootDirInPath } from 'jest-config/build'
-import memoize = require('lodash.memoize')
-import mkdirp = require('mkdirp')
-import { basename, extname, join, normalize, relative } from 'path'
-import { LanguageServiceHost } from 'typescript'
-
-import { ConfigSet } from './config/config-set'
-import { MemoryCache, TsCompiler, TypeInfo } from './types'
-import { Errors, interpolate } from './util/messages'
-import { sha1 } from './util/sha1'
-
-const hasOwn = Object.prototype.hasOwnProperty
-
-/**
- * Register TypeScript compiler.
- * @internal
- */
-export function createCompiler(configs: ConfigSet): TsCompiler {
-  const logger = configs.logger.child({ namespace: 'ts-compiler' })
-  logger.debug(
-    'creating typescript compiler',
-    configs.tsJest.isolatedModules ? '(isolated modules)' : '(language service)',
-  )
-  const cachedir = configs.tsCacheDir
-
-  const memoryCache: MemoryCache = {
-    contents: Object.create(null),
-    versions: Object.create(null),
-    outputs: Object.create(null),
-  }
-
-  // Require the TypeScript compiler and configuration.
-  const ts = configs.compilerModule
-  const cwd = configs.cwd
-
-  const extensions = ['.ts', '.tsx']
-  const {
-    typescript: { options: compilerOptions, fileNames },
-  } = configs
-
-  // Enable `allowJs` when flag is set.
-  if (compilerOptions.allowJs) {
-    extensions.push('.js')
-    extensions.push('.jsx')
-  }
-
-  // Initialize files from TypeScript into project.
-  for (const path of fileNames) memoryCache.versions[path] = 1
-
-  /**
-   * Get the extension for a transpiled file.
-   */
-  const getExtension =
-    compilerOptions.jsx === ts.JsxEmit.Preserve
-      ? (path: string) => (/\.[tj]sx$/.test(path) ? '.jsx' : '.js')
-      : (_: string) => '.js'
-
-  const transformers = configs.tsCustomTransformers
-
-  /**
-   * Create the basic required function using transpile mode.
-   */
-  let getOutput = (code: string, fileName: string /* , lineOffset = 0 */): SourceOutput => {
-    logger.debug({ fileName }, 'getOutput(): compiling as isolated module')
-    const result = ts.transpileModule(code, {
-      fileName,
-      transformers,
-      compilerOptions,
-      reportDiagnostics: configs.shouldReportDiagnostic(fileName),
-    })
-
-    if (result.diagnostics) configs.raiseDiagnostics(result.diagnostics, fileName, logger)
-
-    return [result.outputText, result.sourceMapText as string]
-  }
-
-  let getTypeInfo = (_code: string, _fileName: string, _position: number): TypeInfo => {
-    throw new TypeError(Errors.TypesUnavailableWithoutTypeCheck)
-  }
-
-  // Use full language services when the fast option is disabled.
-  if (!configs.tsJest.isolatedModules) {
-    // Set the file contents into cache.
-    const updateMemoryCache = (code: string, fileName: string) => {
-      logger.debug({ fileName }, `updateMemoryCache()`)
-      if (memoryCache.contents[fileName] !== code) {
-        memoryCache.contents[fileName] = code
-        memoryCache.versions[fileName] = (memoryCache.versions[fileName] || 0) + 1
-      }
-    }
-
-    // Create the compiler host for type checking.
-    const serviceHostDebugCtx = {
-      [LogContexts.logLevel]: LogLevels.debug,
-      namespace: 'ts:serviceHost',
-      call: null,
-    }
-    const serviceHostTraceCtx = {
-      ...serviceHostDebugCtx,
-      [LogContexts.logLevel]: LogLevels.trace,
-    }
-
-    const transformIgnorePattern = (configs.jest.transformIgnorePatterns || JestDefaults.transformIgnorePatterns)
-      .map(pattern => replaceRootDirInPath(configs.rootDir, pattern))
-      .join('|')
-    const transformIgnoreRegExp = new RegExp(transformIgnorePattern)
-
-    const serviceHost: LanguageServiceHost = {
-      getScriptFileNames: () => Object.keys(memoryCache.versions),
-      getScriptVersion: (fileName: string) => {
-        const normalizedFileName = normalize(fileName)
-        const version = memoryCache.versions[normalizedFileName]
-
-        // We need to return `undefined` and not a string here because TypeScript will use
-        // `getScriptVersion` and compare against their own version - which can be `undefined`.
-        // If we don't return `undefined` it results in `undefined === "undefined"` and run
-        // `createProgram` again (which is very slow). Using a `string` assertion here to avoid
-        // TypeScript errors from the function signature (expects `(x: string) => string`).
-        return version === undefined ? ((undefined as any) as string) : String(version)
-      },
-      getScriptSnapshot(fileName: string) {
-        const normalizedFileName = normalize(fileName)
-        const hit = hasOwn.call(memoryCache.contents, normalizedFileName)
-        logger.trace({ normalizedFileName, cacheHit: hit }, `getScriptSnapshot():`, 'cache', hit ? 'hit' : 'miss')
-        // Read contents from TypeScript memory cache.
-        if (!hit) {
-          memoryCache.contents[normalizedFileName] = ts.sys.readFile(normalizedFileName)
-        }
-
-        const contents = memoryCache.contents[normalizedFileName]
-        if (contents === undefined) {
-          return
-        }
-        return ts.ScriptSnapshot.fromString(contents)
-      },
-      fileExists: memoize(ts.sys.fileExists),
-      readFile: logger.wrap(serviceHostTraceCtx, 'readFile', memoize(ts.sys.readFile)),
-      readDirectory: memoize(ts.sys.readDirectory),
-      getDirectories: memoize(ts.sys.getDirectories),
-      directoryExists: memoize(ts.sys.directoryExists),
-      realpath: memoize(ts.sys.realpath!),
-      getNewLine: () => '\n',
-      getCurrentDirectory: () => cwd,
-      getCompilationSettings: () => compilerOptions,
-      getDefaultLibFileName: () => ts.getDefaultLibFilePath(compilerOptions),
-      getCustomTransformers: () => transformers,
-    }
-
-    logger.debug('creating language service')
-    const service = ts.createLanguageService(serviceHost)
-
-    getOutput = (code: string, fileName: string /*, lineOffset = 0 */) => {
-      logger.debug({ fileName }, 'getOutput(): compiling using language service')
-      // Must set memory cache before attempting to read file.
-      updateMemoryCache(code, fileName)
-
-      let output = service.getEmitOutput(fileName)
-
-      if (configs.shouldReportDiagnostic(fileName)) {
-        logger.debug({ fileName }, 'getOutput(): computing diagnostics')
-        // Get the relevant diagnostics - this is 3x faster than `getPreEmitDiagnostics`.
-        const diagnostics = service
-          .getCompilerOptionsDiagnostics()
-          .concat(service.getSyntacticDiagnostics(fileName))
-          .concat(service.getSemanticDiagnostics(fileName))
-
-        // will raise or just warn diagnostics depending on config
-        configs.raiseDiagnostics(diagnostics, fileName, logger)
-      }
-
-      /* istanbul ignore next (this should never happen but is kept for security) */
-      if (output.emitSkipped) {
-        throw new TypeError(`${relative(cwd, fileName)}: Emit skipped`)
-      }
-
-      // if this block executes we have attempted to compile a resolved dependency
-      // that typescript ignored, likely because the file was located in node_modules.
-      // we can force the compiler to retry by invalidating its internal module
-      // resolution cache.
-      //
-      // @see https://github.com/Microsoft/TypeScript/issues/12358
-      // @see https://github.com/microsoft/TypeScript/issues/11946
-      if (output.outputFiles.length === 0 && !transformIgnoreRegExp.test(fileName)) {
-        const normalizedFileName = normalize(fileName)
-
-        // our implementation of getScriptFileNames() depends on the keys
-        // of memoryCache.versions so we must make sure that the file is
-        // in there.
-        if (!hasOwn.call(memoryCache.versions, normalizedFileName)) {
-          memoryCache.versions[normalizedFileName] = 0
-        }
-
-        output = service.getEmitOutput(fileName)
-      }
-
-      // Throw an error when requiring `.d.ts` files.
-      /* istanbul ignore next (this should never happen but is kept for security) */
-      if (output.outputFiles.length === 0) {
-        throw new TypeError(
-          interpolate(Errors.UnableToRequireDefinitionFile, {
-            file: basename(fileName),
-          }),
-        )
-      }
-
-      return [output.outputFiles[1].text, output.outputFiles[0].text]
-    }
-
-    getTypeInfo = (code: string, fileName: string, position: number) => {
-      updateMemoryCache(code, fileName)
-
-      const info = service.getQuickInfoAtPosition(fileName, position)
-      const name = ts.displayPartsToString(info ? info.displayParts : [])
-      const comment = ts.displayPartsToString(info ? info.documentation : [])
-
-      return { name, comment }
-    }
-  }
-
-  const compile = readThrough(cachedir, memoryCache, getOutput, getExtension, cwd, logger)
-  return { cwd, compile, getTypeInfo, extensions, cachedir, ts }
-}
-
-/**
- * Internal source output.
- */
-type SourceOutput = [string, string]
-
-/**
- * Wrap the function with caching.
- */
-function readThrough(
-  cachedir: string | undefined,
-  memoryCache: MemoryCache,
-  compile: (code: string, fileName: string, lineOffset?: number) => SourceOutput,
-  getExtension: (fileName: string) => string,
-  cwd: string,
-  logger: Logger,
-) {
-  if (!cachedir) {
-    return (code: string, fileName: string, lineOffset?: number) => {
-      logger.debug({ fileName }, 'readThrough(): no cache')
-
-      const [value, sourceMap] = compile(code, fileName, lineOffset)
-      const output = updateOutput(value, fileName, sourceMap, getExtension, cwd)
-
-      memoryCache.outputs[fileName] = output
-
-      return output
-    }
-  }
-
-  // Make sure the cache directory exists before continuing.
-  mkdirp.sync(cachedir)
-
-  return (code: string, fileName: string, lineOffset?: number) => {
-    const cachePath = join(cachedir, getCacheName(code, fileName))
-    const extension = getExtension(fileName)
-    const outputPath = `${cachePath}${extension}`
-
-    try {
-      const output = readFileSync(outputPath, 'utf8')
-      if (isValidCacheContent(output)) {
-        logger.debug({ fileName }, 'readThrough(): cache hit')
-        memoryCache.outputs[fileName] = output
-        return output
-      }
-    } catch (err) {}
-
-    logger.debug({ fileName }, 'readThrough(): cache miss')
-    const [value, sourceMap] = compile(code, fileName, lineOffset)
-    const output = updateOutput(value, fileName, sourceMap, getExtension, cwd)
-
-    logger.debug({ fileName, outputPath }, 'readThrough(): writing caches')
-    memoryCache.outputs[fileName] = output
-    writeFileSync(outputPath, output)
-
-    return output
-  }
-}
-
-/**
- * Update the output remapping the source map.
- */
-function updateOutput(
-  outputText: string,
-  fileName: string,
-  sourceMap: string,
-  getExtension: (fileName: string) => string,
-  sourceRoot: string,
-) {
-  const base = basename(fileName)
-  const base64Map = bufferFrom(updateSourceMap(sourceMap, fileName, sourceRoot), 'utf8').toString('base64')
-  const sourceMapContent = `data:application/json;charset=utf-8;base64,${base64Map}`
-  const sourceMapLength = `${base}.map`.length + (getExtension(fileName).length - extname(fileName).length)
-
-  return outputText.slice(0, -sourceMapLength) + sourceMapContent
-}
-
-/**
- * Update the source map contents for improved output.
- */
-function updateSourceMap(sourceMapText: string, fileName: string, _sourceRoot: string) {
-  const sourceMap = JSON.parse(sourceMapText)
-  // const relativeFilePath = posix.normalize(relative(sourceRoot, fileName))
-  // sourceMap.file = relativeFilePath
-  // sourceMap.sources = [relativeFilePath]
-  // sourceMap.sourceRoot = normalize(sourceRoot)
-  sourceMap.file = fileName
-  sourceMap.sources = [fileName]
-  delete sourceMap.sourceRoot
-  return stableStringify(sourceMap)
-}
-
-/**
- * Get the file name for the cache entry.
- */
-function getCacheName(sourceCode: string, fileName: string) {
-  return sha1(fileName, '\x00', sourceCode)
-}
-
-/**
- * Ensure the given cached content is valid by sniffing for a base64 encoded '}'
- * at the end of the content, which should exist if there is a valid sourceMap present.
- */
-function isValidCacheContent(contents: string) {
-  return /(?:9|0=|Q==)$/.test(contents.slice(-3))
-}
diff --git a/src/compiler/__snapshots__/language-service.spec.ts.snap b/src/compiler/__snapshots__/language-service.spec.ts.snap
new file mode 100644
index 0000000000..f12e0f2048
--- /dev/null
+++ b/src/compiler/__snapshots__/language-service.spec.ts.snap
@@ -0,0 +1,40 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`language service should compile js file for allowJs true 1`] = `
+  ===[ FILE: foo.test.js ]========================================================
+  "use strict";
+  Object.defineProperty(exports, "__esModule", { value: true });
+  exports.default = 42;
+  //# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJmaWxlIjoiZm9vLnRlc3QuanMiLCJtYXBwaW5ncyI6Ijs7QUFBQSxrQkFBZSxFQUFFLENBQUEiLCJuYW1lcyI6W10sInNvdXJjZXMiOlsiZm9vLnRlc3QuanMiXSwic291cmNlc0NvbnRlbnQiOlsiZXhwb3J0IGRlZmF1bHQgNDIiXSwidmVyc2lvbiI6M30=
+  ===[ INLINE SOURCE MAPS ]=======================================================
+  file: foo.test.js
+  mappings: ';;AAAA,kBAAe,EAAE,CAAA'
+  names: []
+  sources:
+    - foo.test.js
+  sourcesContent:
+    - export default 42
+  version: 3
+  ================================================================================
+`;
+
+exports[`language service should report diagnostics related to typings with pathRegex config matches file name 1`] = `
+"TypeScript diagnostics (customize using \`[jest-config].globals.ts-jest.diagnostics\` option):
+foo.ts(3,7): error TS2322: Type 'number' is not assignable to type 'string'."
+`;
+
+exports[`language service should use the cache 3`] = `
+  ===[ FILE: src/compiler/language-service.spec.ts ]==============================
+  console.log("hello");
+  //# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJmaWxlIjoiPGN3ZD4vc3JjL2NvbXBpbGVyL2xhbmd1YWdlLXNlcnZpY2Uuc3BlYy50cyIsIm1hcHBpbmdzIjoiQUFBQSxPQUFPLENBQUMsR0FBRyxDQUFDLE9BQU8sQ0FBQyxDQUFBIiwibmFtZXMiOltdLCJzb3VyY2VzIjpbIjxjd2Q+L3NyYy9jb21waWxlci9sYW5ndWFnZS1zZXJ2aWNlLnNwZWMudHMiXSwic291cmNlc0NvbnRlbnQiOlsiY29uc29sZS5sb2coXCJoZWxsb1wiKSJdLCJ2ZXJzaW9uIjozfQ==
+  ===[ INLINE SOURCE MAPS ]=======================================================
+  file: <cwd>/src/compiler/language-service.spec.ts
+  mappings: 'AAAA,OAAO,CAAC,GAAG,CAAC,OAAO,CAAC,CAAA'
+  names: []
+  sources:
+    - <cwd>/src/compiler/language-service.spec.ts
+  sourcesContent:
+    - console.log("hello")
+  version: 3
+  ================================================================================
+`;
diff --git a/src/compiler/__snapshots__/program.spec.ts.snap b/src/compiler/__snapshots__/program.spec.ts.snap
new file mode 100644
index 0000000000..9dad9a5468
--- /dev/null
+++ b/src/compiler/__snapshots__/program.spec.ts.snap
@@ -0,0 +1,44 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`allowJs should compile js file for allowJs true with incremental program 1`] = `
+  ===[ FILE: test-allowJs.test.js ]===============================================
+  "use strict";
+  Object.defineProperty(exports, "__esModule", { value: true });
+  exports.default = 42;
+  //# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJmaWxlIjoidGVzdC1hbGxvd0pzLnRlc3QuanMiLCJtYXBwaW5ncyI6Ijs7QUFBQSxrQkFBZSxFQUFFLENBQUEiLCJuYW1lcyI6W10sInNvdXJjZXMiOlsidGVzdC1hbGxvd0pzLnRlc3QuanMiXSwic291cmNlc0NvbnRlbnQiOlsiZXhwb3J0IGRlZmF1bHQgNDIiXSwidmVyc2lvbiI6M30=
+  ===[ INLINE SOURCE MAPS ]=======================================================
+  file: test-allowJs.test.js
+  mappings: ';;AAAA,kBAAe,EAAE,CAAA'
+  names: []
+  sources:
+    - test-allowJs.test.js
+  sourcesContent:
+    - export default 42
+  version: 3
+  ================================================================================
+`;
+
+exports[`allowJs should compile js file for allowJs true with normal program 1`] = `
+  ===[ FILE: test-allowJs.test.js ]===============================================
+  "use strict";
+  Object.defineProperty(exports, "__esModule", { value: true });
+  exports.default = 42;
+  //# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJmaWxlIjoidGVzdC1hbGxvd0pzLnRlc3QuanMiLCJtYXBwaW5ncyI6Ijs7QUFBQSxrQkFBZSxFQUFFLENBQUEiLCJuYW1lcyI6W10sInNvdXJjZXMiOlsidGVzdC1hbGxvd0pzLnRlc3QuanMiXSwic291cmNlc0NvbnRlbnQiOlsiZXhwb3J0IGRlZmF1bHQgNDIiXSwidmVyc2lvbiI6M30=
+  ===[ INLINE SOURCE MAPS ]=======================================================
+  file: test-allowJs.test.js
+  mappings: ';;AAAA,kBAAe,EAAE,CAAA'
+  names: []
+  sources:
+    - test-allowJs.test.js
+  sourcesContent:
+    - export default 42
+  version: 3
+  ================================================================================
+`;
+
+exports[`typings incremental program should report diagnostics with pathRegex config matches file name 1`] = `"test-typings.ts: Emit skipped"`;
+
+exports[`typings normal program should report diagnostics with pathRegex config matches file name 1`] = `
+"TypeScript diagnostics (customize using \`[jest-config].globals.ts-jest.diagnostics\` option):
+test-typings.ts(3,7): error TS2322: Type 'number' is not assignable to type 'string'."
+`;
diff --git a/src/compiler/__snapshots__/transpile-module.spec.ts.snap b/src/compiler/__snapshots__/transpile-module.spec.ts.snap
new file mode 100644
index 0000000000..de6e87b69b
--- /dev/null
+++ b/src/compiler/__snapshots__/transpile-module.spec.ts.snap
@@ -0,0 +1,47 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`transpile module with isolatedModule: true should compile js file for allowJs true 1`] = `
+  ===[ FILE: src/compiler/transpile-module.spec.ts.test.js ]======================
+  "use strict";
+  Object.defineProperty(exports, "__esModule", { value: true });
+  exports.default = 42;
+  //# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJmaWxlIjoiPGN3ZD4vc3JjL2NvbXBpbGVyL3RyYW5zcGlsZS1tb2R1bGUuc3BlYy50cy50ZXN0LmpzIiwibWFwcGluZ3MiOiI7O0FBQUEsa0JBQWUsRUFBRSxDQUFBIiwibmFtZXMiOltdLCJzb3VyY2VzIjpbIjxjd2Q+L3NyYy9jb21waWxlci90cmFuc3BpbGUtbW9kdWxlLnNwZWMudHMudGVzdC5qcyJdLCJzb3VyY2VzQ29udGVudCI6WyJleHBvcnQgZGVmYXVsdCA0MiJdLCJ2ZXJzaW9uIjozfQ==
+  ===[ INLINE SOURCE MAPS ]=======================================================
+  file: <cwd>/src/compiler/transpile-module.spec.ts.test.js
+  mappings: ';;AAAA,kBAAe,EAAE,CAAA'
+  names: []
+  sources:
+    - <cwd>/src/compiler/transpile-module.spec.ts.test.js
+  sourcesContent:
+    - export default 42
+  version: 3
+  ================================================================================
+`;
+
+exports[`transpile module with isolatedModule: true should compile using transpileModule and not use cache 1`] = `
+  ===[ FILE: src/compiler/transpile-module.spec.ts ]==============================
+  "use strict";
+  Object.defineProperty(exports, "__esModule", { value: true });
+  exports.default = 42;
+  //# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJmaWxlIjoiPGN3ZD4vc3JjL2NvbXBpbGVyL3RyYW5zcGlsZS1tb2R1bGUuc3BlYy50cyIsIm1hcHBpbmdzIjoiOztBQUFBLGtCQUFlLEVBQUUsQ0FBQSIsIm5hbWVzIjpbXSwic291cmNlcyI6WyI8Y3dkPi9zcmMvY29tcGlsZXIvdHJhbnNwaWxlLW1vZHVsZS5zcGVjLnRzIl0sInNvdXJjZXNDb250ZW50IjpbImV4cG9ydCBkZWZhdWx0IDQyIl0sInZlcnNpb24iOjN9
+  ===[ INLINE SOURCE MAPS ]=======================================================
+  file: <cwd>/src/compiler/transpile-module.spec.ts
+  mappings: ';;AAAA,kBAAe,EAAE,CAAA'
+  names: []
+  sources:
+    - <cwd>/src/compiler/transpile-module.spec.ts
+  sourcesContent:
+    - export default 42
+  version: 3
+  ================================================================================
+`;
+
+exports[`transpile module with isolatedModule: true should report diagnostics related to codes with pathRegex config is undefined 1`] = `
+"TypeScript diagnostics (customize using \`[jest-config].globals.ts-jest.diagnostics\` option):
+foo.ts(2,23): error TS1005: '=>' expected."
+`;
+
+exports[`transpile module with isolatedModule: true should report diagnostics related to codes with pathRegex config matches file name 1`] = `
+"TypeScript diagnostics (customize using \`[jest-config].globals.ts-jest.diagnostics\` option):
+foo.ts(2,23): error TS1005: '=>' expected."
+`;
diff --git a/src/compiler/instance.ts b/src/compiler/instance.ts
new file mode 100644
index 0000000000..b168c1ee2e
--- /dev/null
+++ b/src/compiler/instance.ts
@@ -0,0 +1,189 @@
+/**
+ * This code is heavily inspired from
+ * https://github.com/JsCommunity/make-error/blob/v1.3.4/index.js
+ * ...but more modified than expected :-D
+ * Below is the original license anyway:
+ *
+ * ---
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2014 Blake Embrey (hello@blakeembrey.com)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+import { Logger } from 'bs-logger'
+import { readFileSync, writeFileSync } from 'fs'
+import mkdirp = require('mkdirp')
+import { basename, extname, join, normalize } from 'path'
+
+import { ConfigSet } from '../config/config-set'
+import { CompileResult, MemoryCache, TsCompiler } from '../types'
+import { sha1 } from '../util/sha1'
+
+import { compileUsingLanguageService } from './language-service'
+import { compileUsingProgram } from './program'
+import { compileUsingTranspileModule } from './transpile-module'
+
+/**
+ * Update the output remapping the source map.
+ */
+function updateOutput(
+  outputText: string,
+  normalizedFileName: string,
+  sourceMap: string,
+  getExtension: (fileName: string) => string,
+) {
+  const base = basename(normalizedFileName)
+  const base64Map = Buffer.from(updateSourceMap(sourceMap, normalizedFileName), 'utf8').toString('base64')
+  const sourceMapContent = `data:application/json;charset=utf-8;base64,${base64Map}`
+  const sourceMapLength =
+    `${base}.map`.length + (getExtension(normalizedFileName).length - extname(normalizedFileName).length)
+
+  return outputText.slice(0, -sourceMapLength) + sourceMapContent
+}
+
+/**
+ * Update the source map contents for improved output.
+ */
+const updateSourceMap = (sourceMapText: string, normalizedFileName: string): string => {
+  const sourceMap = JSON.parse(sourceMapText)
+  sourceMap.file = normalizedFileName
+  sourceMap.sources = [normalizedFileName]
+  delete sourceMap.sourceRoot
+
+  return JSON.stringify(sourceMap)
+}
+
+/**
+ * Get the file name for the cache entry.
+ */
+const getCacheName = (sourceCode: string, normalizedFileName: string): string => {
+  return sha1(normalizedFileName, '\x00', sourceCode)
+}
+
+/**
+ * Ensure the given cached content is valid by sniffing for a base64 encoded '}'
+ * at the end of the content, which should exist if there is a valid sourceMap present.
+ */
+const isValidCacheContent = (contents: string): boolean => {
+  return /(?:9|0=|Q==)$/.test(contents.slice(-3))
+}
+
+/**
+ * Wrap the function with caching.
+ */
+const readThrough = (
+  cachedir: string | undefined,
+  memoryCache: MemoryCache,
+  compile: CompileResult,
+  getExtension: (fileName: string) => string,
+  logger: Logger,
+) => {
+  if (!cachedir) {
+    return (code: string, fileName: string, lineOffset?: number) => {
+      const normalizedFileName = normalize(fileName)
+      logger.debug({ normalizedFileName }, 'readThrough(): no cache')
+      const [value, sourceMap] = compile(code, normalizedFileName, lineOffset)
+      const output = updateOutput(value, fileName, sourceMap, getExtension)
+      memoryCache.outputs.set(normalizedFileName, output)
+
+      return output
+    }
+  }
+
+  // Make sure the cache directory exists before continuing.
+  mkdirp.sync(cachedir)
+
+  return (code: string, fileName: string, lineOffset?: number) => {
+    const normalizedFileName = normalize(fileName)
+    const cachePath = join(cachedir, getCacheName(code, normalizedFileName))
+    const extension = getExtension(normalizedFileName)
+    const outputPath = `${cachePath}${extension}`
+
+    try {
+      const output = readFileSync(outputPath, 'utf8')
+      if (isValidCacheContent(output)) {
+        logger.debug({ normalizedFileName }, 'readThrough(): cache hit')
+        memoryCache.outputs.set(normalizedFileName, output)
+
+        return output
+      }
+    } catch (err) {}
+
+    logger.debug({ fileName }, 'readThrough(): cache miss')
+    const [value, sourceMap] = compile(code, normalizedFileName, lineOffset)
+    const output = updateOutput(value, normalizedFileName, sourceMap, getExtension)
+
+    logger.debug({ normalizedFileName, outputPath }, 'readThrough(): writing caches')
+    memoryCache.outputs.set(normalizedFileName, output)
+    writeFileSync(outputPath, output)
+
+    return output
+  }
+}
+
+/**
+ * Register TypeScript compiler.
+ * @internal
+ */
+export const createCompiler = (configs: ConfigSet): TsCompiler => {
+  const logger = configs.logger.child({ namespace: 'ts-compiler' })
+  const {
+    typescript: { options: compilerOptions, fileNames },
+    tsJest,
+  } = configs
+  const cachedir = configs.tsCacheDir,
+    ts = configs.compilerModule, // Require the TypeScript compiler and configuration.
+    extensions = ['.ts', '.tsx'],
+    memoryCache: MemoryCache = {
+      contents: new Map<string, string | undefined>(),
+      versions: new Map<string, number>(),
+      outputs: new Map<string, string>(),
+    }
+  // Enable `allowJs` when flag is set.
+  if (compilerOptions.allowJs) {
+    extensions.push('.js')
+    extensions.push('.jsx')
+  }
+  // Initialize files from TypeScript into project.
+  for (const path of fileNames) memoryCache.versions.set(normalize(path), 1)
+  /**
+   * Get the extension for a transpiled file.
+   */
+  const getExtension =
+    compilerOptions.jsx === ts.JsxEmit.Preserve
+      ? (path: string) => (/\.[tj]sx$/.test(path) ? '.jsx' : '.js')
+      : (_: string) => '.js'
+  let compileResult: CompileResult
+  if (!tsJest.isolatedModules) {
+    // Use language services by default
+    if (!tsJest.compilerHost) {
+      compileResult = compileUsingLanguageService(configs, logger, memoryCache)
+    } else {
+      compileResult = compileUsingProgram(configs, logger, memoryCache)
+    }
+  } else {
+    compileResult = compileUsingTranspileModule(configs, logger)
+  }
+  const compile = readThrough(cachedir, memoryCache, compileResult, getExtension, logger)
+
+  return { cwd: configs.cwd, compile, extensions, cachedir, ts }
+}
diff --git a/src/compiler/language-service.spec.ts b/src/compiler/language-service.spec.ts
new file mode 100644
index 0000000000..87e3bf5e07
--- /dev/null
+++ b/src/compiler/language-service.spec.ts
@@ -0,0 +1,119 @@
+import { LogLevels } from 'bs-logger'
+import { removeSync, writeFileSync } from 'fs-extra'
+
+import { makeCompiler } from '../__helpers__/fakers'
+import { logTargetMock } from '../__helpers__/mocks'
+import { tempDir } from '../__helpers__/path'
+import ProcessedSource from '../__helpers__/processed-source'
+
+const logTarget = logTargetMock()
+
+describe('language service', () => {
+  beforeEach(() => {
+    logTarget.clear()
+  })
+
+  it('should use the cache', () => {
+    const tmp = tempDir('compiler'),
+      compiler = makeCompiler({
+        jestConfig: { cache: true, cacheDirectory: tmp },
+        tsJestConfig: { tsConfig: false },
+      }),
+      source = 'console.log("hello")'
+
+    logTarget.clear()
+    const compiled1 = compiler.compile(source, __filename)
+
+    expect(logTarget.filteredLines(LogLevels.debug, Infinity)).toMatchInlineSnapshot(`
+      Array [
+        "[level:20] readThrough(): cache miss
+      ",
+        "[level:20] updateMemoryCache() for language service
+      ",
+        "[level:20] compiler rebuilt Program instance when getting output
+      ",
+        "[level:20] visitSourceFileNode(): hoisting
+      ",
+        "[level:20] getOutput(): computing diagnostics for language service
+      ",
+        "[level:20] invariant: Is service.getProject() identical before and after getting emit output and diagnostics? (should always be true)  true
+      ",
+        "[level:20] readThrough(): writing caches
+      ",
+      ]
+    `)
+
+    logTarget.clear()
+    const compiled2 = compiler.compile(source, __filename)
+
+    expect(logTarget.lines).toMatchInlineSnapshot(`
+      Array [
+        "[level:20] readThrough(): cache hit
+      ",
+      ]
+    `)
+
+    expect(new ProcessedSource(compiled1, __filename)).toMatchSnapshot()
+    expect(compiled2).toBe(compiled1)
+  })
+
+  it('should compile js file for allowJs true', () => {
+    const fileName = `foo.test.js`,
+      compiler = makeCompiler({
+        tsJestConfig: { tsConfig: { allowJs: true, outDir: '$$ts-jest$$' } },
+      }),
+      source = 'export default 42'
+
+    writeFileSync(fileName, source, 'utf8')
+    const compiled = compiler.compile(source, fileName)
+
+    expect(new ProcessedSource(compiled, fileName)).toMatchSnapshot()
+
+    removeSync(fileName)
+  })
+
+  it('should have correct source maps', () => {
+    const compiler = makeCompiler({ tsJestConfig: { tsConfig: false } }),
+      source = 'const g = (v: number) => v\nconst h: number = g(5)'
+
+    const compiled = compiler.compile(source, 'foo.ts')
+
+    expect(new ProcessedSource(compiled, 'foo.ts').outputSourceMaps).toMatchObject({
+      file: 'foo.ts',
+      sources: ['foo.ts'],
+      sourcesContent: [source],
+    })
+  })
+
+  it('should report diagnostics related to typings with pathRegex config matches file name', () => {
+    const fileName = 'foo.ts',
+      source = `
+const g = (v: number) => v
+const x: string = g(5)
+`,
+      compiler = makeCompiler({
+        tsJestConfig: { tsConfig: false, diagnostics: { pathRegex: 'foo.ts' } },
+      })
+    writeFileSync(fileName, source, 'utf8')
+
+    expect(() => compiler.compile(source, fileName)).toThrowErrorMatchingSnapshot()
+
+    removeSync(fileName)
+  })
+
+  it('should not report diagnostics related to typings with pathRegex config does not match file name', () => {
+    const fileName = 'foo.ts',
+      source = `
+const f = (v: number) => v
+const t: string = f(5)
+`,
+      compiler = makeCompiler({
+        tsJestConfig: { tsConfig: false, diagnostics: { pathRegex: 'bar.ts' } },
+      })
+    writeFileSync(fileName, source, 'utf8')
+
+    expect(() => compiler.compile(source, fileName)).not.toThrowError()
+
+    removeSync(fileName)
+  })
+})
diff --git a/src/compiler/language-service.ts b/src/compiler/language-service.ts
new file mode 100644
index 0000000000..2f2261519d
--- /dev/null
+++ b/src/compiler/language-service.ts
@@ -0,0 +1,138 @@
+import { LogContexts, LogLevels, Logger } from 'bs-logger'
+import memoize = require('lodash.memoize')
+import { basename, normalize, relative } from 'path'
+import * as _ts from 'typescript'
+
+import { ConfigSet } from '../config/config-set'
+import { CompileResult, MemoryCache, SourceOutput } from '../types'
+import { Errors, interpolate } from '../util/messages'
+
+/**
+ * @internal
+ */
+export const compileUsingLanguageService = (
+  configs: ConfigSet,
+  logger: Logger,
+  memoryCache: MemoryCache,
+): CompileResult => {
+  const ts = configs.compilerModule,
+    cwd = configs.cwd,
+    { options, fileNames } = configs.typescript,
+    serviceHostTraceCtx = {
+      namespace: 'ts:serviceHost',
+      call: null,
+      [LogContexts.logLevel]: LogLevels.trace,
+    }
+  let projectVersion = 1
+  const serviceHost: _ts.LanguageServiceHost = {
+    getProjectVersion: () => String(projectVersion),
+    getScriptFileNames: () => fileNames,
+    getScriptVersion: (fileName: string) => {
+      const normalizedFileName = normalize(fileName)
+      const version = memoryCache.versions.get(normalizedFileName)
+
+      return version === undefined ? '' : version.toString()
+    },
+    getScriptSnapshot(fileName: string) {
+      const normalizedFileName = normalize(fileName)
+      const hit = memoryCache.contents.has(normalizedFileName)
+      logger.trace({ normalizedFileName, cacheHit: hit }, `getScriptSnapshot():`, 'cache', hit ? 'hit' : 'miss')
+      // Read contents from TypeScript memory cache.
+      if (!hit) {
+        memoryCache.contents.set(normalizedFileName, ts.sys.readFile(normalizedFileName))
+      }
+      const contents = memoryCache.contents.get(normalizedFileName)
+      if (contents === undefined) {
+        return
+      }
+
+      return ts.ScriptSnapshot.fromString(contents)
+    },
+    fileExists: memoize(ts.sys.fileExists),
+    readFile: logger.wrap(serviceHostTraceCtx, 'readFile', memoize(ts.sys.readFile)),
+    readDirectory: memoize(ts.sys.readDirectory),
+    getDirectories: memoize(ts.sys.getDirectories),
+    directoryExists: memoize(ts.sys.directoryExists),
+    realpath: ts.sys.realpath ? memoize(ts.sys.realpath) : undefined,
+    getNewLine: () => '\n',
+    getCurrentDirectory: () => cwd,
+    getCompilationSettings: () => options,
+    getDefaultLibFileName: () => ts.getDefaultLibFilePath(options),
+    getCustomTransformers: () => configs.tsCustomTransformers,
+  }
+
+  logger.debug('compileUsingLanguageService(): creating language service')
+
+  const service: _ts.LanguageService = ts.createLanguageService(
+    serviceHost,
+    ts.createDocumentRegistry(ts.sys.useCaseSensitiveFileNames, cwd),
+  )
+  const updateMemoryCache = (contents: string, normalizedFileName: string): void => {
+    logger.debug({ normalizedFileName }, `updateMemoryCache() for language service`)
+
+    const fileVersion = memoryCache.versions.get(normalizedFileName) ?? 0,
+      isFileInCache = fileVersion !== 0
+    if (!isFileInCache) {
+      fileNames.push(normalizedFileName)
+      // Modifying rootFileNames means a project change
+      projectVersion++
+    }
+    if (memoryCache.contents.get(normalizedFileName) !== contents) {
+      memoryCache.versions.set(normalizedFileName, fileVersion + 1)
+      memoryCache.contents.set(normalizedFileName, contents)
+      // Only bump project version when file is modified in cache, not when discovered for the first time
+      if (isFileInCache) {
+        projectVersion++
+      }
+    }
+  }
+  let previousProgram: _ts.Program | undefined
+
+  return (code: string, fileName: string): SourceOutput => {
+    const normalizedFileName = normalize(fileName)
+    // Must set memory cache before attempting to read file.
+    updateMemoryCache(code, normalizedFileName)
+    const programBefore = service.getProgram()
+
+    if (programBefore !== previousProgram) {
+      logger.debug({ normalizedFileName }, `compiler rebuilt Program instance when getting output`)
+    }
+
+    const output: _ts.EmitOutput = service.getEmitOutput(normalizedFileName)
+    if (configs.shouldReportDiagnostic(normalizedFileName)) {
+      logger.debug({ normalizedFileName }, 'getOutput(): computing diagnostics for language service')
+      // Get the relevant diagnostics - this is 3x faster than `getPreEmitDiagnostics`.
+      const diagnostics = service
+        .getCompilerOptionsDiagnostics()
+        .concat(service.getSyntacticDiagnostics(normalizedFileName))
+        .concat(service.getSemanticDiagnostics(normalizedFileName))
+      // will raise or just warn diagnostics depending on config
+      configs.raiseDiagnostics(diagnostics, normalizedFileName, logger)
+    }
+
+    /* istanbul ignore next (this should never happen but is kept for security) */
+    if (output.emitSkipped) {
+      throw new TypeError(`${relative(cwd, normalizedFileName)}: Emit skipped for language service`)
+    }
+
+    const programAfter = service.getProgram()
+
+    logger.debug(
+      'invariant: Is service.getProject() identical before and after getting emit output and diagnostics? (should always be true) ',
+      programBefore === programAfter,
+    )
+
+    previousProgram = programAfter
+    // Throw an error when requiring `.d.ts` files.
+    /* istanbul ignore next (this should never happen but is kept for security) */
+    if (!output.outputFiles.length) {
+      throw new TypeError(
+        interpolate(Errors.UnableToRequireDefinitionFile, {
+          file: basename(normalizedFileName),
+        }),
+      )
+    }
+
+    return [output.outputFiles[1].text, output.outputFiles[0].text]
+  }
+}
diff --git a/src/compiler/program.spec.ts b/src/compiler/program.spec.ts
new file mode 100644
index 0000000000..91b8e6c988
--- /dev/null
+++ b/src/compiler/program.spec.ts
@@ -0,0 +1,260 @@
+import { LogLevels } from 'bs-logger'
+import { writeFileSync } from 'fs'
+import { removeSync } from 'fs-extra'
+
+import { makeCompiler } from '../__helpers__/fakers'
+import { logTargetMock } from '../__helpers__/mocks'
+import { tempDir } from '../__helpers__/path'
+import ProcessedSource from '../__helpers__/processed-source'
+
+const logTarget = logTargetMock()
+
+const baseTsJestConfig = {
+  compilerHost: true,
+}
+
+describe('typings', () => {
+  const fileName = 'test-typings.ts',
+    source = `
+const f = (v: number) => v
+const t: string = f(5)
+`
+
+  beforeAll(() => {
+    writeFileSync(fileName, source, 'utf8')
+  })
+
+  afterAll(() => {
+    removeSync(fileName)
+  })
+
+  describe('normal program', () => {
+    it('should report diagnostics with pathRegex config matches file name', () => {
+      const compiler = makeCompiler({
+        tsJestConfig: {
+          ...baseTsJestConfig,
+          tsConfig: { incremental: false },
+          diagnostics: { pathRegex: fileName },
+        },
+      })
+
+      expect(() => compiler.compile(source, fileName)).toThrowErrorMatchingSnapshot()
+    })
+
+    it('should not report diagnostics with pathRegex config matches file name', () => {
+      const compiler = makeCompiler({
+        tsJestConfig: {
+          ...baseTsJestConfig,
+          tsConfig: { incremental: false },
+          diagnostics: { pathRegex: 'foo.ts' },
+        },
+      })
+
+      try {
+        compiler.compile(source, fileName)
+      } catch (e) {
+        expect(e).not.toContain('TypeScript diagnostics')
+      }
+    })
+  })
+
+  describe('incremental program', () => {
+    it('should report diagnostics with pathRegex config matches file name', () => {
+      const compiler = makeCompiler({
+        tsJestConfig: {
+          ...baseTsJestConfig,
+          tsConfig: { incremental: true },
+          diagnostics: { pathRegex: 'typings-error.ts' },
+        },
+      })
+
+      expect(() => compiler.compile(source, fileName)).toThrowErrorMatchingSnapshot()
+    })
+
+    it('should not report diagnostics with pathRegex config does not match file name', () => {
+      const compiler = makeCompiler({
+        tsJestConfig: {
+          ...baseTsJestConfig,
+          tsConfig: { incremental: true },
+          diagnostics: { pathRegex: 'foo.ts' },
+        },
+      })
+
+      try {
+        compiler.compile(source, fileName)
+      } catch (e) {
+        expect(e).not.toContain('TypeScript diagnostics')
+      }
+    })
+  })
+})
+
+describe('source-maps', () => {
+  const fileName = 'source-maps-test.ts',
+    source = 'console.log("hello")'
+
+  beforeAll(() => {
+    writeFileSync(fileName, source, 'utf8')
+  })
+
+  afterAll(() => {
+    removeSync(fileName)
+  })
+
+  it('should have correct source maps with normal program', () => {
+    const compiler = makeCompiler({
+      tsJestConfig: {
+        ...baseTsJestConfig,
+        tsConfig: { incremental: false },
+      },
+    })
+
+    const compiled = compiler.compile(source, fileName)
+
+    expect(new ProcessedSource(compiled, fileName).outputSourceMaps).toMatchObject({
+      file: fileName,
+      sources: [fileName],
+      sourcesContent: [source],
+    })
+  })
+
+  it('should have correct source maps with incremental program', () => {
+    const compiler = makeCompiler({
+      tsJestConfig: {
+        ...baseTsJestConfig,
+        tsConfig: { incremental: true },
+      },
+    })
+
+    const compiled = compiler.compile(source, fileName)
+
+    expect(new ProcessedSource(compiled, fileName).outputSourceMaps).toMatchObject({
+      file: fileName,
+      sources: [fileName],
+      sourcesContent: [source],
+    })
+  })
+})
+
+describe('cache', () => {
+  const tmp = tempDir('compiler'),
+    fileName = 'test-cache.ts',
+    source = 'console.log("hello")'
+
+  beforeAll(() => {
+    writeFileSync(fileName, source, 'utf8')
+  })
+
+  afterAll(() => {
+    removeSync(fileName)
+  })
+
+  it('should use the cache with normal program', () => {
+    const compiler = makeCompiler({
+      jestConfig: { cache: true, cacheDirectory: tmp },
+      tsJestConfig: {
+        ...baseTsJestConfig,
+        tsConfig: { incremental: false },
+      },
+    })
+
+    logTarget.clear()
+    const compiled1 = compiler.compile(source, fileName)
+    expect(logTarget.filteredLines(LogLevels.debug, Infinity)).toMatchInlineSnapshot(`
+      Array [
+        "[level:20] readThrough(): cache miss
+      ",
+        "[level:20] updateMemoryCache() for program
+      ",
+        "[level:20] visitSourceFileNode(): hoisting
+      ",
+        "[level:20] getOutput(): computing diagnostics for program
+      ",
+        "[level:20] readThrough(): writing caches
+      ",
+      ]
+    `)
+
+    logTarget.clear()
+    const compiled2 = compiler.compile(source, fileName)
+    expect(logTarget.lines).toMatchInlineSnapshot(`
+      Array [
+        "[level:20] readThrough(): cache hit
+      ",
+      ]
+    `)
+
+    expect(compiled2).toBe(compiled1)
+  })
+
+  it('should use the cache with normal program', () => {
+    const compiler = makeCompiler({
+      jestConfig: { cache: true, cacheDirectory: tmp },
+      tsJestConfig: {
+        ...baseTsJestConfig,
+        tsConfig: { incremental: true },
+      },
+    })
+
+    logTarget.clear()
+    const compiled1 = compiler.compile(source, fileName)
+    expect(logTarget.filteredLines(LogLevels.debug, Infinity)).toMatchInlineSnapshot(`
+Array [
+  "[level:20] readThrough(): cache miss
+",
+  "[level:20] updateMemoryCache() for program
+",
+  "[level:20] visitSourceFileNode(): hoisting
+",
+  "[level:20] getOutput(): computing diagnostics for incremental program
+",
+  "[level:20] readThrough(): writing caches
+",
+]
+`)
+
+    logTarget.clear()
+    const compiled2 = compiler.compile(source, fileName)
+    expect(logTarget.lines).toMatchInlineSnapshot(`
+      Array [
+        "[level:20] readThrough(): cache hit
+      ",
+      ]
+    `)
+
+    expect(compiled2).toBe(compiled1)
+  })
+})
+
+describe('allowJs', () => {
+  const fileName = 'test-allowJs.test.js',
+    source = 'export default 42'
+
+  beforeAll(() => {
+    writeFileSync(fileName, source, 'utf8')
+  })
+
+  afterAll(() => {
+    removeSync(fileName)
+  })
+
+  it('should compile js file for allowJs true with normal program', () => {
+    const compiler = makeCompiler({
+      tsJestConfig: { ...baseTsJestConfig, tsConfig: { allowJs: true, outDir: '$$ts-jest$$', incremental: false } },
+    })
+
+    const compiled = compiler.compile(source, fileName)
+
+    expect(new ProcessedSource(compiled, fileName)).toMatchSnapshot()
+  })
+
+  it('should compile js file for allowJs true with incremental program', () => {
+    const compiler = makeCompiler({
+      tsJestConfig: { ...baseTsJestConfig, tsConfig: { allowJs: true, outDir: '$$ts-jest$$', incremental: true } },
+    })
+
+    const compiled = compiler.compile(source, fileName)
+
+    expect(new ProcessedSource(compiled, fileName)).toMatchSnapshot()
+  })
+})
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
new file mode 100644
index 0000000000..b7822a9c33
--- /dev/null
+++ b/src/compiler/program.ts
@@ -0,0 +1,178 @@
+import { LogContexts, LogLevels, Logger } from 'bs-logger'
+import memoize = require('lodash.memoize')
+import { basename, normalize, relative } from 'path'
+import * as _ts from 'typescript'
+
+import { ConfigSet } from '../config/config-set'
+import { CompileResult, MemoryCache, SourceOutput } from '../types'
+import { Errors, interpolate } from '../util/messages'
+
+/**
+ * @internal
+ */
+export const compileUsingProgram = (configs: ConfigSet, logger: Logger, memoryCache: MemoryCache): CompileResult => {
+  logger.debug('compileUsingProgram(): create typescript compiler')
+
+  const ts = configs.compilerModule,
+    cwd = configs.cwd,
+    { options, fileNames, projectReferences, errors } = configs.typescript
+  const compilerHostTraceCtx = {
+      namespace: 'ts:compilerHost',
+      call: null,
+      [LogContexts.logLevel]: LogLevels.trace,
+    },
+    sys = {
+      ...ts.sys,
+      readFile: logger.wrap(compilerHostTraceCtx, 'readFile', memoize(ts.sys.readFile)),
+      readDirectory: logger.wrap(compilerHostTraceCtx, 'readDirectory', memoize(ts.sys.readDirectory)),
+      getDirectories: logger.wrap(compilerHostTraceCtx, 'getDirectories', memoize(ts.sys.getDirectories)),
+      fileExists: logger.wrap(compilerHostTraceCtx, 'fileExists', memoize(ts.sys.fileExists)),
+      directoryExists: logger.wrap(compilerHostTraceCtx, 'directoryExists', memoize(ts.sys.directoryExists)),
+      resolvePath: logger.wrap(compilerHostTraceCtx, 'resolvePath', memoize(ts.sys.resolvePath)),
+      realpath: ts.sys.realpath ? logger.wrap(compilerHostTraceCtx, 'realpath', memoize(ts.sys.realpath)) : undefined,
+      getCurrentDirectory: () => cwd,
+      getNewLine: () => '\n',
+      getCanonicalFileName: (fileName: string) =>
+        ts.sys.useCaseSensitiveFileNames ? fileName : fileName.toLowerCase(),
+    }
+  let builderProgram: _ts.EmitAndSemanticDiagnosticsBuilderProgram, program: _ts.Program, host: _ts.CompilerHost
+  // Fallback for older TypeScript releases without incremental API.
+  if (options.incremental) {
+    host = ts.createIncrementalCompilerHost(options, sys)
+    builderProgram = ts.createIncrementalProgram({
+      rootNames: fileNames.slice(),
+      options,
+      host,
+      configFileParsingDiagnostics: errors,
+      projectReferences,
+    })
+    program = builderProgram.getProgram()
+  } else {
+    host = {
+      ...sys,
+      getSourceFile: (fileName, languageVersion) => {
+        const contents = ts.sys.readFile(fileName)
+
+        if (contents === undefined) return
+
+        return ts.createSourceFile(fileName, contents, languageVersion)
+      },
+      getDefaultLibFileName: () => ts.getDefaultLibFilePath(options),
+      useCaseSensitiveFileNames: () => sys.useCaseSensitiveFileNames,
+    }
+    program = ts.createProgram({
+      rootNames: fileNames.slice(),
+      options,
+      host,
+      configFileParsingDiagnostics: errors,
+      projectReferences,
+    })
+  }
+  // Read and cache custom transformers.
+  const customTransformers = configs.tsCustomTransformers,
+    updateMemoryCache = (contents: string, normalizedFileName: string): void => {
+      logger.debug({ normalizedFileName }, `updateMemoryCache() for program`)
+
+      const fileVersion = memoryCache.versions.get(normalizedFileName) ?? 0,
+        isFileInCache = fileVersion !== 0
+      // Add to `rootFiles` when discovered for the first time.
+      if (!isFileInCache) {
+        fileNames.push(normalizedFileName)
+      }
+      // Avoid incrementing cache when nothing has changed.
+      if (memoryCache.contents.get(normalizedFileName) !== contents) {
+        memoryCache.versions.set(normalizedFileName, fileVersion + 1)
+        memoryCache.contents.set(normalizedFileName, contents)
+      }
+      const sourceFile = options.incremental
+        ? builderProgram.getSourceFile(normalizedFileName)
+        : program.getSourceFile(normalizedFileName)
+      // Update program when file changes.
+      if (
+        sourceFile === undefined ||
+        sourceFile.text !== contents ||
+        program.isSourceFileFromExternalLibrary(sourceFile)
+      ) {
+        const programOptions = {
+          rootNames: fileNames.slice(),
+          options,
+          host,
+          configFileParsingDiagnostics: errors,
+          projectReferences,
+        }
+        if (options.incremental) {
+          builderProgram = ts.createIncrementalProgram(programOptions)
+          program = builderProgram.getProgram()
+        } else {
+          program = ts.createProgram(programOptions)
+        }
+      }
+    }
+
+  return (code: string, fileName: string): SourceOutput => {
+    const normalizedFileName = normalize(fileName),
+      output: [string, string] = ['', '']
+    // Must set memory cache before attempting to read file.
+    updateMemoryCache(code, normalizedFileName)
+    const sourceFile = options.incremental
+      ? builderProgram.getSourceFile(normalizedFileName)
+      : program.getSourceFile(normalizedFileName)
+
+    if (!sourceFile) throw new TypeError(`Unable to read file: ${fileName}`)
+
+    const result: _ts.EmitResult = options.incremental
+      ? builderProgram.emit(
+          sourceFile,
+          (path, file, _writeByteOrderMark) => {
+            output[path.endsWith('.map') ? 1 : 0] = file
+          },
+          undefined,
+          undefined,
+          customTransformers,
+        )
+      : program.emit(
+          sourceFile,
+          (path, file, _writeByteOrderMark) => {
+            output[path.endsWith('.map') ? 1 : 0] = file
+          },
+          undefined,
+          undefined,
+          customTransformers,
+        )
+    if (configs.shouldReportDiagnostic(normalizedFileName)) {
+      logger.debug(
+        { normalizedFileName },
+        `getOutput(): computing diagnostics for ${options.incremental ? 'incremental program' : 'program'}`,
+      )
+      const diagnostics = ts.getPreEmitDiagnostics(program, sourceFile).slice()
+      // will raise or just warn diagnostics depending on config
+      configs.raiseDiagnostics(diagnostics, normalizedFileName, logger)
+    }
+
+    if (result.emitSkipped) {
+      throw new TypeError(`${relative(cwd, fileName)}: Emit skipped`)
+    }
+
+    // Throw an error when requiring files that cannot be compiled.
+    if (output[0] === '') {
+      if (program.isSourceFileFromExternalLibrary(sourceFile)) {
+        throw new TypeError(`Unable to compile file from external library: ${relative(cwd, fileName)}`)
+      }
+
+      throw new TypeError(
+        interpolate(Errors.UnableToRequireDefinitionFile, {
+          file: basename(normalizedFileName),
+        }),
+      )
+    }
+    if (configs.tsJest.emit && options.incremental) {
+      process.on('exit', () => {
+        // Emits `.tsbuildinfo` to filesystem.
+        // @ts-ignore
+        program.emitBuildInfo()
+      })
+    }
+
+    return output
+  }
+}
diff --git a/src/compiler/transpile-module.spec.ts b/src/compiler/transpile-module.spec.ts
new file mode 100644
index 0000000000..5c1ed108b6
--- /dev/null
+++ b/src/compiler/transpile-module.spec.ts
@@ -0,0 +1,130 @@
+import { LogLevels } from 'bs-logger'
+import { removeSync, writeFileSync } from 'fs-extra'
+
+import { makeCompiler } from '../__helpers__/fakers'
+import { logTargetMock } from '../__helpers__/mocks'
+import ProcessedSource from '../__helpers__/processed-source'
+
+const logTarget = logTargetMock()
+
+describe('transpile module with isolatedModule: true', () => {
+  const baseTsJestConfig = {
+    isolatedModules: true,
+  }
+
+  beforeEach(() => {
+    logTarget.clear()
+  })
+
+  it('should compile using transpileModule and not use cache', () => {
+    const compiler = makeCompiler({ tsJestConfig: { ...baseTsJestConfig, tsConfig: false } }),
+      spy = jest.spyOn(require('typescript'), 'transpileModule')
+
+    logTarget.clear()
+    const compiled = compiler.compile('export default 42', __filename)
+
+    expect(new ProcessedSource(compiled, __filename)).toMatchSnapshot()
+    expect(spy).toHaveBeenCalled()
+    expect(logTarget.filteredLines(LogLevels.debug, Infinity)).toMatchInlineSnapshot(`
+      Array [
+        "[level:20] readThrough(): no cache
+      ",
+        "[level:20] getOutput(): compiling as isolated module
+      ",
+        "[level:20] visitSourceFileNode(): hoisting
+      ",
+      ]
+    `)
+
+    spy.mockRestore()
+  })
+
+  it('should compile js file for allowJs true', () => {
+    const fileName = `${__filename}.test.js`,
+      compiler = makeCompiler({
+        tsJestConfig: { ...baseTsJestConfig, tsConfig: { allowJs: true, outDir: '$$ts-jest$$' } },
+      }),
+      source = 'export default 42'
+
+    writeFileSync(fileName, source, 'utf8')
+    const compiled = compiler.compile(source, fileName)
+
+    expect(new ProcessedSource(compiled, fileName)).toMatchSnapshot()
+
+    removeSync(fileName)
+  })
+
+  it('should have correct source maps', () => {
+    const compiler = makeCompiler({ tsJestConfig: { ...baseTsJestConfig, tsConfig: false } }),
+      source = 'const f = (v: number) => v\nconst t: number = f(5)'
+
+    const compiled = compiler.compile(source, __filename)
+
+    expect(new ProcessedSource(compiled, __filename).outputSourceMaps).toMatchObject({
+      file: __filename,
+      sources: [__filename],
+      sourcesContent: [source],
+    })
+  })
+
+  it('should not report diagnostics related to typings', () => {
+    const compiler = makeCompiler({ tsJestConfig: { ...baseTsJestConfig, tsConfig: false } })
+
+    expect(() =>
+      compiler.compile(
+        `
+const f = (v: number) => v
+const t: string = f(5)
+const v: boolean = t
+`,
+        'foo.ts',
+      ),
+    ).not.toThrowError()
+  })
+
+  it('should report diagnostics related to codes with pathRegex config is undefined', () => {
+    const compiler = makeCompiler({ tsJestConfig: { ...baseTsJestConfig, tsConfig: false } })
+
+    expect(() =>
+      compiler.compile(
+        `
+const f = (v: number) = v
+const t: string = f(5)
+`,
+        'foo.ts',
+      ),
+    ).toThrowErrorMatchingSnapshot()
+  })
+
+  it('should report diagnostics related to codes with pathRegex config matches file name', () => {
+    const compiler = makeCompiler({
+      tsJestConfig: { ...baseTsJestConfig, tsConfig: false, diagnostics: { pathRegex: 'foo.ts' } },
+    })
+
+    expect(() =>
+      compiler.compile(
+        `
+const f = (v: number) = v
+const t: string = f(5)
+`,
+        'foo.ts',
+      ),
+    ).toThrowErrorMatchingSnapshot()
+  })
+
+  it('should not report diagnostics related to codes with pathRegex config does not match file name', () => {
+    const compiler = makeCompiler({
+      tsJestConfig: { ...baseTsJestConfig, tsConfig: false, diagnostics: { pathRegex: 'bar.ts' } },
+    })
+
+    expect(() =>
+      compiler.compile(
+        `
+const f = (v: number) = v
+const t: string = f(5)
+`,
+        'foo.ts',
+      ),
+    ).not.toThrowError()
+  })
+})
diff --git a/src/compiler/transpile-module.ts b/src/compiler/transpile-module.ts
new file mode 100644
index 0000000000..8ca30bc4e5
--- /dev/null
+++ b/src/compiler/transpile-module.ts
@@ -0,0 +1,30 @@
+import { Logger } from 'bs-logger'
+import { normalize } from 'path'
+
+import { ConfigSet } from '../config/config-set'
+import { CompileResult, SourceOutput } from '../types'
+
+/**
+ * @internal
+ */
+export const compileUsingTranspileModule = (configs: ConfigSet, logger: Logger): CompileResult => {
+  logger.debug('compileUsingTranspileModule(): create typescript compiler')
+
+  return (code: string, fileName: string): SourceOutput => {
+    logger.debug({ fileName }, 'getOutput(): compiling as isolated module')
+
+    const normalizedFileName = normalize(fileName)
+    const result = configs.compilerModule.transpileModule(code, {
+      fileName: normalizedFileName,
+      transformers: configs.tsCustomTransformers,
+      compilerOptions: configs.typescript.options,
+      reportDiagnostics: configs.shouldReportDiagnostic(normalizedFileName),
+    })
+
+    if (result.diagnostics && configs.shouldReportDiagnostic(normalizedFileName)) {
+      configs.raiseDiagnostics(result.diagnostics, normalizedFileName, logger)
+    }
+
+    return [result.outputText, result.sourceMapText!]
+  }
+}
diff --git a/src/config/__snapshots__/config-set.spec.ts.snap b/src/config/__snapshots__/config-set.spec.ts.snap
index 57ee18fee6..bb58b30cc6 100644
--- a/src/config/__snapshots__/config-set.spec.ts.snap
+++ b/src/config/__snapshots__/config-set.spec.ts.snap
@@ -42,6 +42,7 @@ Object {
   "tsJest": Object {
     "babelConfig": undefined,
     "compiler": "typescript",
+    "compilerHost": false,
     "diagnostics": Object {
       "ignoreCodes": Array [
         6059,
@@ -51,6 +52,7 @@ Object {
       "pretty": true,
       "throws": true,
     },
+    "emit": false,
     "isolatedModules": false,
     "packageJson": Object {
       "kind": "file",
@@ -67,7 +69,6 @@ Object {
     "inlineSources": true,
     "module": 1,
     "noEmit": false,
-    "outDir": "$$ts-jest$$",
     "removeComments": false,
     "sourceMap": true,
     "target": 1,
@@ -131,6 +132,7 @@ exports[`tsJest should return correct defaults 1`] = `
 Object {
   "babelConfig": undefined,
   "compiler": "typescript",
+  "compilerHost": false,
   "diagnostics": Object {
     "ignoreCodes": Array [
       6059,
@@ -140,6 +142,7 @@ Object {
     "pretty": true,
     "throws": true,
   },
+  "emit": false,
   "isolatedModules": false,
   "packageJson": Object {
     "kind": "file",
diff --git a/src/config/config-set.spec.ts b/src/config/config-set.spec.ts
index a9a18c06fb..3683f768c3 100644
--- a/src/config/config-set.spec.ts
+++ b/src/config/config-set.spec.ts
@@ -45,7 +45,7 @@ function createConfigSet({
   resolve?: ((path: string) => string) | null
   [key: string]: any
 } = {}) {
-  const cs = new ConfigSet(fakers.jestConfig(jestConfig, tsJestConfig), parentConfig)
+  const cs = new ConfigSet(fakers.getJestConfig(jestConfig, tsJestConfig), parentConfig)
   if (resolve) {
     cs.resolvePath = resolve
   }
@@ -893,7 +893,6 @@ Array [
 `)
     expect(compiler.ts).toBe(cs.compilerModule)
     expect(typeof compiler.compile).toBe('function')
-    expect(typeof compiler.getTypeInfo).toBe('function')
   })
 }) // tsCompiler
 
@@ -967,7 +966,7 @@ describe('cacheKey', () => {
     cs.jsonValue.value = val
     // digest is mocked in src/__mocks__/index.ts
     expect(cs.cacheKey).toMatchInlineSnapshot(
-      '"{\\"digest\\":\\"a0d51ca854194df8191d0e65c0ca4730f510f332\\",\\"jest\\":{\\"__backported\\":true,\\"globals\\":{}},\\"projectDepVersions\\":{\\"dev\\":\\"1.2.5\\",\\"opt\\":\\"1.2.3\\",\\"peer\\":\\"1.2.4\\",\\"std\\":\\"1.2.6\\"},\\"transformers\\":[\\"hoisting-jest-mock@1\\"],\\"tsJest\\":{\\"compiler\\":\\"typescript\\",\\"diagnostics\\":{\\"ignoreCodes\\":[6059,18002,18003],\\"pretty\\":true,\\"throws\\":true},\\"isolatedModules\\":false,\\"packageJson\\":{\\"kind\\":\\"file\\"},\\"transformers\\":[]},\\"tsconfig\\":{\\"declaration\\":false,\\"inlineSourceMap\\":false,\\"inlineSources\\":true,\\"module\\":1,\\"noEmit\\":false,\\"outDir\\":\\"$$ts-jest$$\\",\\"removeComments\\":false,\\"sourceMap\\":true,\\"target\\":1}}"',
+      `"{\\"digest\\":\\"a0d51ca854194df8191d0e65c0ca4730f510f332\\",\\"jest\\":{\\"__backported\\":true,\\"globals\\":{}},\\"projectDepVersions\\":{\\"dev\\":\\"1.2.5\\",\\"opt\\":\\"1.2.3\\",\\"peer\\":\\"1.2.4\\",\\"std\\":\\"1.2.6\\"},\\"transformers\\":[\\"hoisting-jest-mock@1\\"],\\"tsJest\\":{\\"compiler\\":\\"typescript\\",\\"compilerHost\\":false,\\"diagnostics\\":{\\"ignoreCodes\\":[6059,18002,18003],\\"pretty\\":true,\\"throws\\":true},\\"emit\\":false,\\"isolatedModules\\":false,\\"packageJson\\":{\\"kind\\":\\"file\\"},\\"transformers\\":[]},\\"tsconfig\\":{\\"declaration\\":false,\\"inlineSourceMap\\":false,\\"inlineSources\\":true,\\"module\\":1,\\"noEmit\\":false,\\"removeComments\\":false,\\"sourceMap\\":true,\\"target\\":1}}"`,
     )
   })
 }) // cacheKey
diff --git a/src/config/config-set.ts b/src/config/config-set.ts
index f58b61e7d3..c39d5bea61 100644
--- a/src/config/config-set.ts
+++ b/src/config/config-set.ts
@@ -24,7 +24,7 @@ import {
 } from 'typescript'
 
 import { digest as MY_DIGEST, version as MY_VERSION } from '..'
-import { createCompiler } from '../compiler'
+import { createCompiler } from '../compiler/instance'
 import { internals as internalAstTransformers } from '../transformers'
 import {
   AstTransformerDesc,
@@ -265,15 +265,18 @@ export class ConfigSet {
     // parsed options
     const res: TsJestConfig = {
       tsConfig,
+      compilerHost: options.compilerHost ?? false,
+      emit: options.emit ?? false,
       packageJson,
       babelConfig,
       diagnostics,
       isolatedModules: !!options.isolatedModules,
-      compiler: options.compiler || 'typescript',
+      compiler: options.compiler ?? 'typescript',
       transformers,
       stringifyContentPathRegex,
     }
     this.logger.debug({ tsJestConfig: res }, 'normalized ts-jest config')
+
     return res
   }
 
@@ -530,17 +533,15 @@ export class ConfigSet {
       // we don't want to create declaration files
       declaration: false,
       noEmit: false,
-      outDir: '$$ts-jest$$',
       // else istanbul related will be dropped
       removeComments: false,
       // to clear out else it's buggy
       out: undefined,
       outFile: undefined,
-      composite: undefined,
+      composite: undefined, // see https://github.com/TypeStrong/ts-node/pull/657/files
       declarationDir: undefined,
       declarationMap: undefined,
       emitDeclarationOnly: undefined,
-      incremental: undefined,
       sourceRoot: undefined,
       tsBuildInfoFile: undefined,
     }
@@ -628,6 +629,8 @@ export class ConfigSet {
   }
 
   /**
+   * Load TypeScript configuration. Returns the parsed TypeScript config and
+   * any `tsConfig` options specified in ts-jest tsConfig
    * @internal
    */
   readTsConfig(
diff --git a/src/ts-jest-transformer.ts b/src/ts-jest-transformer.ts
index 30a51f2ce5..17b5658ae0 100644
--- a/src/ts-jest-transformer.ts
+++ b/src/ts-jest-transformer.ts
@@ -92,6 +92,7 @@ export class TsJestTransformer implements Transformer {
       jestConfig: new JsonableValue(jestConfigObj),
       configSet,
     })
+
     return configSet
   }
 
@@ -127,6 +128,7 @@ export class TsJestTransformer implements Transformer {
       result = source
     } else if (isJsFile || isTsFile) {
       // transpile TS code (source maps are included)
+      /* istanbul ignore if */
       result = configs.tsCompiler.compile(source, filePath)
     } else {
       // we should not get called for files with other extension than js[x], ts[x] and d.ts,
@@ -163,6 +165,7 @@ export class TsJestTransformer implements Transformer {
    * @param fileContent The content of the file
    * @param filePath The full path to the file
    * @param jestConfigStr The JSON-encoded version of jest config
+   * @param transformOptions
    * @param transformOptions.instrument Whether the content will be instrumented by our transformer (always false)
    * @param transformOptions.rootDir Jest current rootDir
    */
@@ -176,6 +179,7 @@ export class TsJestTransformer implements Transformer {
     const configs = this.configsFor(jestConfigStr)
     // we do not instrument, ensure it is false all the time
     const { instrument = false, rootDir = configs.rootDir } = transformOptions
+
     return sha1(
       configs.cacheKey,
       '\x00',
diff --git a/src/types.ts b/src/types.ts
index 241e2ca310..1b5b8e75f2 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -37,6 +37,20 @@ export interface TsJestGlobalOptions {
    */
   isolatedModules?: boolean
 
+  /**
+   * Use TypeScript's compiler host API.
+   *
+   * @default false
+   */
+  compilerHost?: boolean
+
+  /**
+   * Emit compiled files into `.ts-jest` directory
+   *
+   * @default false
+   */
+  emit?: boolean
+
   /**
    * Compiler to use (default to 'typescript'):
    */
@@ -57,8 +71,16 @@ export interface TsJestGlobalOptions {
     | boolean
     | {
         pretty?: boolean
+        /**
+         * Ignore TypeScript warnings by diagnostic code.
+         */
         ignoreCodes?: number | string | (number | string)[]
         pathRegex?: RegExp | string
+        /**
+         * Logs TypeScript errors to stderr instead of throwing exceptions.
+         *
+         * @default false
+         */
         warnOnly?: boolean
       }
 
@@ -119,11 +141,12 @@ export interface TsJestConfig {
   tsConfig: TsJestConfig$tsConfig
   packageJson: TsJestConfig$packageJson
   isolatedModules: boolean
+  compilerHost: boolean
+  emit: boolean
   compiler: string
   diagnostics: TsJestConfig$diagnostics
   babelConfig: TsJestConfig$babelConfig
   transformers: string[]
-
   // to deprecate / deprecated === === ===
   stringifyContentPathRegex: TsJestConfig$stringifyContentPathRegex
 }
@@ -159,33 +182,31 @@ export interface TSCommon {
   formatDiagnosticsWithColorAndContext: typeof _ts.formatDiagnosticsWithColorAndContext
 }
 
-/**
- * Track the project information.
- * @internal
- */
-export interface MemoryCache {
-  contents: { [path: string]: string | undefined }
-  versions: { [path: string]: number | undefined }
-  outputs: { [path: string]: string }
-}
-
-/**
- * Information retrieved from type info check.
- */
-export interface TypeInfo {
-  name: string
-  comment: string
-}
-
 export interface TsCompiler {
   cwd: string
   extensions: string[]
   cachedir: string | undefined
   ts: TSCommon
   compile(code: string, fileName: string, lineOffset?: number): string
-  getTypeInfo(code: string, fileName: string, position: number): TypeInfo
 }
 
+/**
+ * Internal source output.
+ */
+export type SourceOutput = [string, string]
+
+/**
+ * Track the project information.
+ * @internal
+ */
+export interface MemoryCache {
+  contents: Map<string, string | undefined>
+  versions: Map<string, number>
+  outputs: Map<string, string>
+}
+
+export type CompileResult = (code: string, fileName: string, lineOffset?: number) => SourceOutput
+
 export interface AstTransformerDesc {
   name: string
   version: number
diff --git a/src/util/messages.ts b/src/util/messages.ts
index 33939b8af4..028141ee35 100644
--- a/src/util/messages.ts
+++ b/src/util/messages.ts
@@ -3,12 +3,12 @@
 /**
  * @internal
  */
-export enum Errors {
+export const enum Errors {
   LoadingModuleFailed = 'Loading module {{module}} failed with error: {{error}}',
   UnableToLoadOneModule = 'Unable to load the module {{module}}. {{reason}} To fix it:\n{{fix}}',
   UnableToLoadAnyModule = 'Unable to load any of these modules: {{module}}. {{reason}}. To fix it:\n{{fix}}',
   TypesUnavailableWithoutTypeCheck = 'Type information is unavailable with "isolatedModules"',
-  UnableToRequireDefinitionFile = 'Unable to require `.d.ts` file.\nThis is usually the result of a faulty configuration or import. Make sure there is a `.js`, `.json` or another executable extension available alongside `{{file}}`.',
+  UnableToRequireDefinitionFile = 'Unable to require `.d.ts` file for file: {{file}}.\nThis is usually the result of a faulty configuration or import. Make sure there is a `.js`, `.json` or another executable extension available alongside `{{file}}`.',
   FileNotFound = 'File not found: {{inputPath}} (resolved as: {{resolvedPath}})',
   UntestedDependencyVersion = "Version {{actualVersion}} of {{module}} installed has not been tested with ts-jest. If you're experiencing issues, consider using a supported version ({{expectedVersion}}). Please do not report issues in ts-jest if you are using unsupported versions.",
   MissingDependency = "Module {{module}} is not installed. If you're experiencing issues, consider installing a supported version ({{expectedVersion}}).",
@@ -27,7 +27,7 @@ export enum Errors {
 /**
  * @internal
  */
-export enum Helps {
+export const enum Helps {
   FixMissingModule = '{{label}}: `npm i -D {{module}}` (or `yarn add --dev {{module}}`)',
   IgnoreDiagnosticCode = 'customize using `[jest-config].globals.ts-jest.diagnostics` option',
   MigrateConfigUsingCLI = 'Your Jest configuration is outdated. Use the CLI to help migrating it: ts-jest config:migrate <config-file>.',
@@ -36,7 +36,7 @@ export enum Helps {
 /**
  * @internal
  */
-export enum Deprecateds {
+export const enum Deprecateds {
   EnvVar = 'Using env. var "{{old}}" is deprecated, use "{{new}}" instead.',
   ConfigOption = '"[jest-config].{{oldPath}}" is deprecated, use "[jest-config].{{newPath}}" instead.',
   ConfigOptionWithNote = '"[jest-config].{{oldPath}}" is deprecated, use "[jest-config].{{newPath}}" instead.\n    ↳ {{note}}',
@@ -47,7 +47,7 @@ export enum Deprecateds {
 /**
  * @internal
  */
-export enum ImportReasons {
+export const enum ImportReasons {
   TsJest = 'Using "ts-jest" requires this package to be installed.',
   BabelJest = 'Using "babel-jest" requires this package to be installed.',
 }
diff --git a/tslint.json b/tslint.json
index 7669513b00..e21fb54d77 100644
--- a/tslint.json
+++ b/tslint.json
@@ -47,6 +47,7 @@
     "no-string-throw": true,
     "no-var-keyword": true,
     "object-literal-sort-keys": false,
+    "one-variable-per-declaration": false,
     "ordered-imports": [
       true,
       {